A large portion of found oil and reserves can be characterized as heavy oil or bitumen, which is distinguished by a particularly high asphaltene or maltene fraction. These oils are often produced as emulsions with water when using secondary recovery techniques. Because heavy oils are ordinarily low cost feedstocks, there is often an economic incentive to convert these heavy oils (or other refractory hydrocarbons, such as coal derived liquids) into gasoline boiling range liquid fuels if processing costs can be kept low. This invention relates generally to an improved process for upgrading these heavy oils and bitumen into fuels or marketable syncrudes.
Considerable process technology already exists for upgrading heavy crudes, bitumens, and coal liquids, but most of the known processes are expensive and/or inefficient. Among those broad categories of primary heavy oil upgrading processes already known in the art are: carbon rejection or demetallation processes, hydrogen addition processes, and gasification or combustion processes.
Carbon rejection processes include delayed coking, Flexicoking, visbreaking, Fluidized Catalytic Cracking (FCC) (with the use of metals tolerant catalysts), Reduced Crude Cracking (RCC), and other versions of heavy oil cracking. A particular example of a carbon rejection process which may be used as a pre-treatment in advance of other upgrading steps is the Asphaltene Residual Treating (ART) process, which removes Conradson carbon fractions and metals components at otherwise low conversion.
An example of a gasification process is the gasification process developed by Texaco Development Corporation. This is a non-catalytic partial oxidation gasification process for generating principally hydrogen and carbon monoxide from mixtures of vacuum residue, SDA pitch, or other low hydrogen-to-carbon ratio feedstocks with water.
Hydrogen addition processes include: LC-fining, H-Oil, the Shell Resid Process, resid hydrocracking, resid hydrodesulfurization (HDS), and hydrodenitrogenation (HDN), most of which have been demonstrated on a commercial scale. Second generation hydrogen addition processes include: Microcat-RC, CANMET hydrovisbreaking, Veba Combi-cracking, and Dynacracking, all of which have been demonstrated primarily on a semi-commercial scale.
The advantages and disadvantages of these processes, as well as their general economics, are known in the art. For example, one significant disadvantage, particularly of carbon rejection processes, is the ordinarily high yield of coke or metals-containing solids which must be disposed of at considerable expense and some risk of environmental hazard. Additionally, gasification processes, such as the Texaco process, usually result in low liquid yields. Moreover, to achieve economically viable operation, these processes often require a scale which is much larger than the size needed to match the production rate of a particular heavy oil production site. Additionally, emulsified oils often must be demulsified prior to further processing.
Both hydrogen addition and carbon rejection processes, which often require the use of large quantities of solid catalysts, are also susceptible to reduced throughput and high catalyst replacement costs resulting from catalyst poisoning when processing heavy oils. This poisoning usually results from the deposition of either contaminant metals, high molecular weight refractory compounds (or coke derived therefrom), or sulfur or nitrogen containing heterocyclic compounds onto the catalyst surface. A review of this phenomenon is published in Applied Catalysis, (1985) 15, 197,225. Under certain circumstances these strongly-adsorbed poisons can react with catalyst components to form low melting eutectic compositions which can either sinter molecular sieves, zeolites, or other high surface area catalyst components or effectively block catalyst pores, in either case significantly reducing catalyst effectiveness. Additionally, beneficial acidic components can be partially neutralized and catalytic metallic components blocked by this virtually irreversible metals adsorption. Asphaltene and some resin fractions contain significant quantities of such poisons, which can be "cracked" onto the catalyst at high temperatures. Consequently, even though asphaltenes often comprise only 12% to 15% of typical heavy oil feedstocks, they disproportionally contribute to solid catalyst deactivation.
The following is a summary of the major problems encountered while upgrading heavy oils, bitumens, coal liquids, and other low hydrogen-to-carbon ratio feedstocks, by known refinery processes:
1. Severe reaction conditions are required. PA0 2. Poor liquid yields with high gas and coke makes. PA0 3 Formation of a poor quality coke which is not marketable. PA0 4. High costs and materials-handling concerns associated with the use of hydrogen. PA0 5. Deactivation of solid catalysts by contaminant metals, basic nitrogen compounds, and/or sulfur compounds. A separate processing step may be required to remove such compounds. PA0 6. Required disposal of metals-laden solid catalysts, often as hazardous wastes. PA0 7. Demulsification often being required prior to processing. PA0 8. High viscosity feed produced requiring cutback with light solvents which must be sacrificed during subsequent processing. PA0 9. Low volatility of heavy oils limits throughput in vapor phase processes. PA0 1. Increased liquid yields of high-octane gasoline blending (aromatic) components. PA0 2. Decreased hydrogen consumption. PA0 3. Low yield of light gas cracking products. PA0 4. Partial desulfurization of feed. PA0 5. Mild operating conditions. PA0 6. Avoidance of large quantities of metal laden solid catalysts requiring disposal as hazardous waste. PA0 7. Long catalyst life in the presence of contaminant metals often found in residua. PA0 8. Ability to use emulsified oils directly in process without pre-demulsification step. PA0 1. U.K. Patent GB2 132 107 A, Feb. 3, 1982, Huibers, et al., assigned to Hydrocarbon Research, Inc. (HRI). PA0 2. U.K. Patent GB 2094 827 A, Feb. 3, 1982, Huibers, et al., assigned to Hydrocarbon Research, Inc. (HRI). PA0 3. U.S. Pat. No. 4,446,070, May 1, 1984, Huibers, et al., assigned to Hydrocarbon Research, Inc. (HRI). PA0 4. U.S. Pat. Nos. 4,496,778 and 4,496,779, Jan. 29, 1985, Myers, et al., both assigned to Exxon Research & Engineering Co.